I discovered a problem with my new residential radiant heating system. The system is designed to use differential pressure to control the main circulator pump. The objective is to maintain constant water pressure across the heating circuits as the flow changes due to the opening and closing of zone valves.
The contractor supplied a Grundfos variable speed pump and a box that measures differential pressure. Both devices can be set for 0-10V or 20ma interface. Unfortunately the contractor thought this would yield a fixed pressure. It does not. The motor has a simple triac speed control on what appears to be their standard AC motor. The pressure sensor only measures. It provides 0-10 with either a positive or negative change in output that represents the pressure.
I need to do something to fix that. I have spent a bunch of hours on the web so far and I am having real trouble uncovering data and particularly prices. I think I need a PID controller to look at the presure signal and control the motor speed. This needs to be as inexpensive as possible. It would mount on the wall and would need a case to keep inspectors happy. It does not need a display. Once set up it will just run. The control should also have one additional 24VAC input for looking at the heat demand signal and setting the output voltage to 0 when no heat is needed. Or just drop 120V power to the motor.
Can anyone tell me if this is indeed the approach I need and make some recommendations for a unit. It needs to be very simple to set up. I simply do not have the time to write a lot of code from scratch after learning the language. I am working full time on other things on the way late house.
Any help appreciated.
The contractor supplied a Grundfos variable speed pump and a box that measures differential pressure. Both devices can be set for 0-10V or 20ma interface. Unfortunately the contractor thought this would yield a fixed pressure. It does not. The motor has a simple triac speed control on what appears to be their standard AC motor. The pressure sensor only measures. It provides 0-10 with either a positive or negative change in output that represents the pressure.
I need to do something to fix that. I have spent a bunch of hours on the web so far and I am having real trouble uncovering data and particularly prices. I think I need a PID controller to look at the presure signal and control the motor speed. This needs to be as inexpensive as possible. It would mount on the wall and would need a case to keep inspectors happy. It does not need a display. Once set up it will just run. The control should also have one additional 24VAC input for looking at the heat demand signal and setting the output voltage to 0 when no heat is needed. Or just drop 120V power to the motor.
Can anyone tell me if this is indeed the approach I need and make some recommendations for a unit. It needs to be very simple to set up. I simply do not have the time to write a lot of code from scratch after learning the language. I am working full time on other things on the way late house.
Any help appreciated.